Coin Change II LC 518: DP Count Ways (Unbounded)
Medium DP/unbounded knapsack: dp[x]+=dp[x-c] counts coin change ways (no permutations). O(n·amount) time, O(amount) space. Practice now.
Combination Sum
Given an array of distinct integers and a target, return all unique combinations where the chosen numbers sum to target (elements may be reused)
Word Break II (LC 140) — DFS + Memo DP (Hard)
Solve LeetCode 140 Word Break II with DFS + memoization DP. Output-sensitive (≈O(n²)+answers). Step-by-step for interviews—practice now.